function getXMLHttpRequest()
{    
	var httprequest="";
	 if(window.XMLHttpRequest)
        {
           httprequest=new XMLHttpRequest();
           if(httprequest.overrideMimeType)
           {
              httprequest.overrideMimeType("text/xml");
           }         
        }
        else if(window.ActiveXObject)
        {
           try
           {
              httprequest=new ActiveXObject("Msxml2.XMLHTTP");
           }
           catch(e)
           {
              try
              {
                 httprequest=new ActiveXObject("Microsoft.XMLHTTP");
              }
              catch(e)
              {
               
              }
           }
        }
        
        if(!httprequest)
        {
          alert("??httprequest?????");
          return false;
        }
        return httprequest;
}